This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2001-316148 filed in JAPAN on Oct. 15, 2001, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a process for producing a golf ball. More particularly, the present invention relates to an improvement in the compression molding processes of a golf ball or a spherical body that forms a part of a golf ball.
2. Description of the Related Art
There exist solid golf balls having a variety of layered structures. For example, there are one-piece golf balls including a single layer, two-piece golf balls including a cover and a core having a single-layered structure, and multi-piece golf balls including a cover and a core having a two-layered structure. The core has a two-layered structure including a center and a mid layer covering over the center. Any of the one-piece golf balls, the cores for a two-piece golf ball, and the centers and the cores for a multi-piece golf ball are spherical bodies, which are usually formed from a rubber composition.
When a core having a two-layered structure is formed, a mold is provided comprising upper and lower portions, both of which having a number of hemispheric cavities. Then, a center and rubber composition which surrounds the center are placed into a cavity (usually the cavity of the lower portion). The total volume of the rubber composition and the center is greater than the volume of the core. As the mold is gradually clamped, excess rubber composition flows out from the cavities. Concomitant with the outflow of the rubber composition, air is also discharged from the cavities. The mold is completely clamped and heated to a predetermined temperature, and then kept for a predetermined period. A crosslinking reaction of the rubber cures the rubber composition, and thus a mid layer is formed. Thereafter, the mold is unclamped, and the core is removed from the cavity. The rubber composition which had flowed out from the cavity is also cured to some extent providing a residue around the cavity in the shape of a ring. The cured matter is referred to as “molding flash.” The molding flash is removed from the mold.
Because the mold has a number of cavities as described above, a number of molding flashes having a ring-shape are also formed. The number of molding flashes which are formed are identical with the number of cavities. Usually, from 4 to 100 molding flashes are formed per one mold. Adjacent molding flashes contact each other and become integrated. Therefore, all of the molding flashes are serially connected to result in the formation of a sheet-like shape. If an operator grasps and pulls a part of the molding flashes, the entire flash can be readily removed at once.
Upon clamping, if a large amount of the rubber composition flows out in an omnidirectional manner, adjacent molding flashes can be integrated together without fail. However, the outflow of a large amount of rubber composition leads directly to a decreased process yield, thereby elevating the cost of producing a golf ball. To the contrary, in instances where the amount of the rubber composition outflow is suppressed, some parts of the adjacent molding flashes are not integrated, if the amount of the outflow varies in dependence upon the direction. Accordingly, working property is deteriorated in removing the molding flash. In addition, varying amount of the outflow also leads to deviation of mass of the mid layer (uneven wall thickness).
Problems involving a deteriorated working property when removing the molding flash are also raised upon the compression molding of one-piece golf balls and the cores for a two-piece golf ball, the centers for a multi-piece golf ball, and the like.